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Wideband timing of the double pulsar (PSR J0737-3039A) Grandy, Victoria Rebecca

Abstract

Pulsars are neutron stars (NS) that produce beamed radio-frequency emission. Due to their rapid, steady rotation rate, this signal is detected as a series of pulses whose integrated profile is unusually stable over time. Pulsars in double neutron star (DNS) binary systems are a rare, but extremely useful, astronomical tool and have been used in tests of gravity theories in the strong-gravitational field limit. Rarer still are DNS systems in which both objects have been detected as pulsars; only one such system has been found thus far -- PSR J0737-3039A/B. Discovered over a decade ago, this system consists of one recycled pulsar, PSR J0737-3039A, and its companion, PSR J0737-3039B, which has since become undetectable. In any pulsar-related research, precise timing is necessary to produce meaningful results. The pulse time of arrivals (TOAs) are greatly affected by the medium through which the electromagnetic (EM) signal travels in both frequency-dependent and -independent ways. Even after accounting for such effects, many pulse profiles still exhibit frequency-dependent shape changes, which can greatly affect the precision of the timing results. Traditionally, corrections are applied to the TOAs after calculation in an ad hoc manner. In contrast to this, we explored the wideband timing algorithm developed by Timothy T. Pennucci and collaborators which accounts for frequency-dependent profile changes through a two-dimensional Gaussian pulse portrait model implemented in the TOA calculations. It was found that the portrait model is well-representative of the pulse profile shape over a wide frequency range. This method is also able to produce a robust set of wideband TOAs. The subsequent timing model, determined with TEMPO timing software, was found to be comparable to those produced from subbanded TOAs derived though more traditional methods. Some inconsistencies between the timing model astrometric and spin parameters of the wideband and subbanded data of this well-studied pulsar imply potential difficulties in achieving precise timing results not only for this pulsar, but for others, such as those used in pulsar timing arrays aiming to detect gravitational waves.

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